This invention concerns a reagent for blood analysis especially suitable for use in measurement of leukocyte count in a blood by means of an automatic blood-analysis instrument.
Ingredients of blood are closely related with a whole organization or internal organs of human body. Therefore, analytical data of blood are important as an index of diagnosis or treatment. Especially, leukocytes of blood include many useful informations for diagnosis or treatment of organism, since they show a rapid response to variations of organism conditions.
Up to now, leukocyte classification which is carried out by classifying leukocytes into 5 to 8 kinds and counting them has been practiced as an inspection of leukocytes. However, since this inspection depends on visual count by a microscope, the inspection including pretreatment takes comparatively many hours. Further, the determination of visual count demands the expert.
On the other hand, operations of inspection based on leukocyte classification have been partially automated by introducing the pattern-recognition technology of a computer. However, even if the partial automation is possible, the final determination of the inspection is depended on the expert, and it takes many hours for the inspection. Further, large-sized and expensive instruments are demanded for the inspection.
Recently, the automatic blood-analysis instrument which is equipped with a mechanism for counting blood corpuscles such as leukocyte, red corpuscles, platelets and so on has developed to accomplish simplicity and rapidity of the blood analysis. The blood count is carried out by an electric resistance system as shown in FIG. 6. According to this system, the blood is diluted with a diluent 1, and therefore the blood corpuscles 2 are dispersed in the diluent 1. When negative pressure is added in a detector 3, the dispersed blood corpuscles 2 are sucked in the detector 3 through a small hole 4. In that case, outer and inner sides of the detector 3 are provided with outer and inner electrodes 5, 6, respectively, so that a certain current is flowed from the outer electrode 5 to the inner electrode 6. When the blood corpuscles 2 of which the electric resistance is extremely larger than that of the electrolyte (the diluent 1) are passed through the small hole 4, the resistance between both electrodes is changed. Such a change of resistance is taken out as a signal to count the blood corpuscles such as leukocytes.
Before making leukocyte count by means of the electric resistance system, the blood is diluted to a certain dilution magnification, and a certain amount of a lysing reagent for leukocyte count is added. The lysing reagent solves erythrocytes and cytoplasm of leukocytes, and leaves the nuclei to be counted. The nuclei is passed through the small hole 4 of the detector 4.
However, in the traditional practice for counting leukocytes, since a surface active reagent having the strong lyse-force is used as a lysing reagent, all of leukocytes to be counted arrive at the neighborhood of contraction limit, so that total count only, i.e. one-peak fractionation in size distribution as shown in FIG. 7, has been carried out.
In order to improve the one-peak fractionation and to emphasize the difference of the particle size inherent in leukocytes, the lysing reagent capable of slowing the contraction speed of large particles and rapidly contracting small particles such as lymphoid cells has been developed. This lysing reagent contains, as a main ingredient, dodecyltrimethylammonium chloride and tetradecyltrimethylammonium bromide, and thus accomplishes two-peaks fractionation by means of a blood corpuscle counter. This fractionation if called as a discrimination histogram of the populations of lymphoid and myeloid cells or a leukocyte volume histogram. A pattern of two-peaks fractionation is shown in FIG. 8.
Such a blood analysis practiced by the automatic blood-analysis instrument has an advantage that other measuring items, such as erythrocyte number, hemoglobin amount, hematocrit value, platelet number and so on, as well as leukocyte, can be simultaneously measured in a short time. However with respect to leukocyte count, two-peaks fractionation was unsatisfactory in comparison with the practical 6 items classification. Thus, it has been demanded to raise the fractionation number.